Method of making paramagnetic materials



METHOD OF MAKING PARAMAGNETIC MATERIALS Filed Jan. 31, 1940 Enventor Chandler l Vnt orth attorney Patented Nov. 4, i941 METHOD OF ame. PARAMAGNETIC MATERIALS Chandler Wentworth, Haddon Heights, N.J., as-

signor to Radio Corporation of America, a corporation of Delaware Application January 31, 1940, Serial No. 3l6;692 g a 2 Claims. (01.148-1) This invention relates to the manufacture of cores and other structures formed of comminuted paramagnetic materials.

The prior art recognizes that structures formed of curved or'spherical magnetic or paramagnetic particles exhibit a higher resistance to eddy current losses than similar structures formed of irregular or angular particles of the same material. This is so because such curved ,or spher-' ical particles-can be insulated and compressed into a coherent structure with a minimum of damage to the insulation which must necessarily be present between the individual particles in the finished Structure.

While various methods are known for producing such nonangular particles, the usual methods suffer the common disadvantage that their practice results in the production of particles which are coated with an oxide of the metal or alloy of which the particles are formed. It is of course true that such oxide coatings may be utilized as the insulating material which serves to electrically isolate the individual particles in the finished structure; however, the very presence of such oxides results in a structure of lower permeability than would be the case if certain other more efllcient insulating material were to be emp oved.

Accordingly, the principal object of the present invention is to provide an improved method of "What is claimed is:

producing unoxidized spherical or curved parathe powdered particles as by gently agitating a sieve 2 or the like in which the batch is contained. The separate particles are rendered molten by' contact with a hot gaseous medium emanating from a flaming liquid fuel 3 such, for example, as alcohol, contained in-a tank or receptacle 4. It may be that the particles, upon having the sieve, enter a gaseous strata or zone A wherein they are subject to some degree of oxidation. If this is indeed the case. the oxide or oxides are efiectively reduced upon the conversion of the particles to the molten state, say in the second zone B. It is while in the molten state that the particles assume a curved or substantially spherical contourwhich is preserved upon their partial solidification during their passage through the lower temperatures prevailing in the nonoxidizlng gaseous zone 0 immediately above the alcohol or other non-aqueous liquid 3 in which they are collected and cooled.

After the now cool rounded or spherical metallic particlesare removed from the nonoxidizing medium in which they are'collected, they may v be coated with an insulating substance of a type calculated to ensure high permeability. Among the recommended insulating coating materials are iron and zinc salts, which may be formed by treating the particles with phosphoric acid containing some (say 12% by weight) zinc.

1. Method of making paramagnetic particles of substantially curved contour which comprises dropping separate molten particles of a magnetic material into flaming alcohol.

a 2. Method of making unoxidized paramagnetic particles of substantially curved. contour which comprises subjecting separate comminuted particles of a magnetic material to an alcohol flame to render said particles molten and then solidify ingsaid particlesinfluid alcohol. I f cmmmaa vvnu'rwoa'ra. 

